1. Field of the Invention
The present invention relates to a light source unit and a projector.
2. Description of the Related Art
Currently, data projectors are used on many occasions as image projection units which project the screen of a personal computer and video images, as well as images based on image data stored in a memory card or the like to a screen. Conventionally, the mainstream of these projectors has been those which use as a light source a high-intensity discharge lamp. In recent years, however, there have been made many developments or proposals of projectors which use as a light source a light emitting diode (LED), a laser light emitting element, an organic EL or a luminescent material.
Additionally, there have been made developments on light sources and projectors which increase the light utilization efficiency by taking into consideration the chip-shapes and light distribution characteristics depending upon colors of red, green and blue LED chips. For example, Japanese Unexamined Patent Publication No. 2011-53323 filed by the applicant of this patent application discloses a light source unit including an excitation light source which emits light in the blue wavelength band by using a laser diode, a luminescent wheel (a rotary plate) that has a layer of a luminescent material which absorbs light emitted from the excitation light source to transform it into visible green light and a diffusive transmission layer which diffusively transmits light emitted from the excitation light source and which is driven to rotate by a motor, and a light emitting diode which emits red light, and a projector which includes this light source unit.
Additionally, Japanese Unexamined Patent Publication No. 2004-341105 proposes a light source unit in which red, green and blue luminescent material layers are laid in an end-to-end fashion on a front surface of a light emitting plate made up of a light transmissive disk while a dichroic filter which transmits ultraviolet light and reflects visible light is disposed on a rear surface of the light emitting plate, whereby lights in the red, green and blue wavelength bands are produced by shining ultraviolet light onto the luminescent material layers from a rear surface side of the light emitting plate.
In the light source unit described above, however, since the directions in which the lights in the red, green and blue wavelength bands are emitted from their emitting point are different from each other, an optical layout necessary to turn optical axes of the red, green and blue lights into the same direction for illumination of the display element becomes complex. This complex optical layout increases the numbers of lenses and mirrors and interrupts the attempt to reduce the production costs and size of the projector.